1. Field of the Invention
This invention relates generally to control of a power supply. More particularly the invention relates to control of a switching mode power stage supplying power to either a fixed load or a variable load.
2. Brief Description of Prior Art
Charge-mode controllers for switch mode power supplies are very desirable as they provide a fast response to transients in the load and high immunity to switching noise. Also it can increase the power supply output impedance to prevent oscillation with negative impedance loads.
Analog charge-mode controllers for a switching mode power supply have been designed to deal with the significant problem of instability caused by variations in the load and the duty cycle of the power supply. Depending upon the load impedance and the duty-cycle of the gate drive signal for the switch in the voltage converter of the power supply, an analog charge-mode controller and a voltage converter can go unstable and begin to oscillate. A discussion of this problem with analog charge-mode controllers is reported in an article entitled “Charge Control: Modeling Analysis and Design” by W. Tang, F. C. Lee, R. Ridley, and I. Cohen, at the Proceedings of IEEE Power Electronics Specialists' Conference, 1992, pp. 503-511.
What is needed is a stable charge-mode controller for a switch mode power stage. The controller and power stage should have a wide bandwidth capable of handling any load condition. Such a controller and power stage would enable many new processes and many new systems from hand-held electronic devices to hybrid engine systems.